There are many possible reasons why women may not ovulate regularly. Some women have a signaling problem between the brain and the ovaries, meaning that the normal hormone pathways do not operate effectively. This results in no signs of ovulation, irregular, rare, or absent ovulation.
This is common in women who exercise at a very high level and in underweight women. It is also common in women who engage in shift work, such as flight attendants.
Some women have polycystic ovarian syndrome (PCOS), a very common hormonal condition associated with long cycles or infrequent or absent periods, the excess activity of some hormones.
Other hormonal imbalances may also cause irregular ovulation, such as abnormalities of prolactin secretion or of thyroid function.
Another serious cause of ovulation failure is premature menopause. This may be temporary or permanent. When the ovaries have exhausted their supply of eggs, this usually results in premature menopause. This condition will not respond to ovulation induction medication and your fertility specialist may discuss the use of donor eggs.
There may be a significant problem within the ovaries with the development of premature ovarian failure and damage to the little eggs and follicles. This can be temporary or permanent and is the only sort of ovulation problem which is not helped by the use of ovulation induction medications.